Preparing metallurgical fuel from noncaking coal utilizing air-blown pitch binder



Aug. 28, 1962 E. GoRlN ETAL 3,051,628

PREPARING METALLURGICAL FUEL FROM NON-CAKING COAL UTILIZING AIR-BLOWN PITCH BINDER Filed July 22, 1960 mjom OO FmDGEm 0 MV mm mmv H m m NN R Em w fl mo m G F T Iv. T T E R m V 0 E R B m .mE OO mrwn Q ,a ATTORNEY 3,051,628 PREPARING METALLURGCAL FUEL FRW NGN- CAKING CUAL UTILlZllJG AR-BLWN FITCH BBNDER Everett Gorin, Pittsburgh, and Robert 3. Friedrich, Finleyville, Pa., assigncrs to Consolidation Coai Company, Pittsburgh, Pa., a corporation of Pennsylvania Fiied July 22, 1960, Ser. No. 44,602 4 Claims. (Cl. 202-26) The present invention relates to the preparation of metallurgical fuel from non-caking and weakly caking bituminous and sub-bituminous coal.

The present application is a continuation-in-part of s our copending 4application Serial No. 746,990, filed July 7', 1958, and assigned to the assignee of the present lin- Vention.

There are substantial reserves of non-caking coals throughout the world which, because of their non-caking property, cannot be converted into metallurgical fuels by conventional coking processes. Attempts have been made to utilize non-caking coals in the production of metallurgical coke by a process sequence involving: rst, low temperature carbonization of the coal to yield a solid distiilation residue known as char; second, briquetting the resulting char with suitable binders; and third, coking and calcining the prepared briquets. Coke produced in this TABLE I Properties of Typical Non-Cakz'ng Coal Proximate analysis: Weight percent Moisture 19.20 Volatile matter 38.44 Fixed carbon 39.68 Ash 2.68

Ultimate analysis (moisture-free basis): Weight percent 5.02

' The high percentage of oxygen in the coal is characteristic of non-caking coals. Non-caking coal, when heated to elevated temperatures, merely crumbles and evolves gases and tar vapors. It does not soften to form agglomerate particles which would form a strong cellular coke, but instead leaves a soft powdery mass as a residue. Numerous well-known tests have been developed to distinguish caking coals from non-caking coals. Lowry, The Chemistry of Coal Utilization, vol. I (1945), pages 73, 77-79.

Non-caking coal can be comminuted to a fluidizable size and carbonized at low temperature (850 to 1100 F.) to produce gas, tar and a char residue. Because the starting coal is non-caking, no preliminary decaking treatment is required and hence substantial tar yield can be achieved.

By preliminarilyshrinking the char from a non-caking .A fm,

coal prior to briquet formation, the adverse effects of differential shrinkage can be avoided and coke of satisfactory strength can be prepared. The char can be shrunk by heating it to an elevated temperature at which particle contraction occurs. This elevated temperature of shrinking will oe above the temperature at which the char Was generated from the starting coal, and, in general, Will be in the range lof 1350 to 1800 F. The shrinking treatment is accompanied by devolatilization of the char which yields substantial quantities of combustible gases rich in hydrogen and methane.

it is possible to prepare coked briquets of satisfactory metallurgical strength by directly carbonizing, devolatilizing and shrinking the non-caking coal in a'single high temperature carbonization treatment. However, the yield of tar from high temperature carbonization is inadequate to provide autogenously the pitch binder requirements of the subsequent briquet formulation. Low temperature carbonization at temperatures from about 800 to 1l00 F. maximizes the yield of tar and assures the provision of the required amount of pitch binder. However, the pitch obtained directly from low temperature carbonization of a non-caking or weakly caking coal, unfortunately, does not possess satisfactory binder properties for briquet formulations. While resort may be had to other materials to serve as binders. It would be highly desirable from an economic standpoint to obtain a suitable binder from the coal utilized as feed to the briquetting operation.

Accordingly, the primary object of this invention is to provide a process for making `strong briquets from a noncaking or weakly caking coal, wherein essentially all the requisite ingredients of the briquets are derived from the coal itself.

Another object of this invention is to provide a process for making ya suitable binder for briquet formulations from a non-caking or weakly caking coal.

Other objects and advantages of our invention will become apparent upon reference to the following description and to the accompanying drawing in which there is shown a schematic flow diagram illustrating apparatus adapted to the practice of the invention.

-In accordance with the present invention, we are able to make strong briquets solely from ingredients derived from a non-caking coal. Our process briefly comprises carbonizing the coal at low temperatures to yield Vchar and tar. The char is further heated to an elevated temperature to effect shrinkage. The tar is fractionated to recover high boiling pitch, middle distillate oil, and a low boiling fraction. The pitch is blown with air at elevated temperature to increase its xed carbon content to 25 to 50 percent. A portion of the middle distillate oil may be blended, if necessary, with the air blown pitch to reduce the melting point of the pitch. The resulting blend is mixed with the preshrunk char and formed into raw briquets which are thereafter calcined to yield a strong briquet as product.

Referring now to the drawing for a description of the preferred embodhnent ofV our invention, the principal apparatus includes a coal Crusher l10, a fluidized coal dryer 11, a fluidized low temperature carbonization vessel 12., a surge vessel for product char 13, a briquet calcining vessel 14, a hot char quenching vessel 15, a kneading apparatus 16 for briquet formulation, a briquet making apparatus i7, a tar condenser 18, a tar decanter vessel 19, a tar distillation vessel Z0, a pitch air blowing Vessel 21 and a briquet binder mixing vessel 22.

The starting coal is introduced into the coal crusher 10 where it is comminuted to a uidizable size, for example, capable of passing through a l4-1nesh Tyler Standard speneae screen. vA `typical particle size distribution (Wetscreen analysis) for a comminuted non-caking coal is:

TABLE H Particle Size Distribution` Suitably comminuted non-caking coal is recoveredV from the coal crusher and transferred through a conduit 23 into the yfluidized coal dryer 11. Hot gases for uidizing and drying the coal are generated in a combustion vessel 24 and by combustion ofY fuel gas with air introduced through conduits 25 and 26 respectively. The hot combustion gases are transferred through a conduit 27 for drying and preheating the comminuted coal in the dryer 11. Since the coal is non-caking, the dryer 11 may also serve as a preheater. Accordingly, the coal is not only dehydrated but also preheated in the dryer 11 to a temperature of about 30G-600 F. The

Vspent tluidizing gases are removed from the dryer 11 through a conduit 28. VPreferably any entrained solids in the spent'fluidizing gases are recovered by passing the gasesV from the conduit 2S through suitable recovery equipment. v

the carbonization temperature at which it was generated results in further devolatilization of 4the char yielding Y one-half to two hours.

- 'Preheated dehydrated coal is recovered from thevdryer i 11 through a conduit 29 and is introduced intoY the fluidized' low temperature carbonization vessel V12. The coal is maintainedpin a uidized state in the uidized lowtemperature'carbonization vessel 12Y at a Vtemperature of about 800 to ll00 F. (preferably about 850 to 950,F.). Air, employed as the fluidizing gas, is introduced through a'conduit 30. The coal is maintained in the low car-f bonization vessel 12 for about l0 to 60 Vminutes until substantially complete tar evolution has occurred. Gases, tar vapors and oxygen-depleted air are recovered through a conduit 31 and are transferred to the tar condenser Vessel 18 for further treatment to be hereinafter described. Y

The heat required for carbonization is supplied by partial combustion of the coal with the oxygen content ofthe fluidizing air. Because of the non-caking property of the starting coal, there is no tendency for particle size agglomeration. Accordingly, the product char, recovered through a conduit 32, 'has a free-flowing particulateV character.

The product char is transferred without deliberate cooling through the conduitl 32 into the product char surge vessel 13. The char is maintained within the surge vessel 13 substantially at the carbonization'temperature. One portion of the product char is withdrawn through a conduit 33 andintroduced intoV a char burner 34 for turbulent contact therein with air from a conduit 35. The partially burned-char and air are transferred at an elevated temperature as a dilutephase suspension from the burner 34 into a transfer conduit 36. The remainder of the char-from the surge vesselV 13'is'withdrawn through a conduit 33a and introduced into the transfer conduit 36 to supplement the dilute phase suspension of heated'char and air. The final temperature of the dilute phase stream must be sufficient to effect the desiredV char shrinking, i.e., from about 1350 to l800 F. Hence the air and char stream leaving the char burner 34 should be at atemperature of about 1600 to 2250 F. The preshrinking treatment of the char permits production of briquets therefrom which will possess satisfactory high temperature strength following suitable calcining treatment. Heating of the char to temperatures above significant quantities of combustibleV devolatilization gases rich in hydrogen and methane.v

The calcining treatment for briquets occurs Within the calciner vessel 14. Cold, freshly produced briquets are introduced into the top of the calciner vessel 14 through a conduit 37. The briquets pass downwardly through the calciner vessel 14 and are contacted with the dilute phase suspension of hot preshrunk char in hot gases. The preshrunk char and gases are cooled and the briquets are heated by heat interchange Within the calciner vessel 14. The briquets, following calcining, are withdrawn from the bottom of the calciner vessel 14V through a conduit 3S at a temperature between 1400 and 1700 F., preferably aboutV l600 F, The final briquet temperature, of course, is lower .than the temperature of the dilute phase suspension of shrunk char and gases which enters the calciner vessel 14 through the transfer conduit 36. Y

The fresh briquets which enter the calciner vessel 14 are at first heated Vvery rapidly, i.e., shock-heated, by Virtue of their sudden exposure to the elevated temperatures therein. Thereafter the briquets are more slowly heated to calcining temperatures'. The residence time of the briquets in the calciner vessel preferably is from about This rapid initial heating serves toV coke the briquet binder quickly and to set the binder as a matrix for confining the char particles. Appreciable quantities of tar Vvapors are evolved during this coking. The tar vapors are carried lalong with the heated gases Vand entrained shrunk char. Y The dilute phase suspension of shrunk char is recovered from the topfof the calciner vessel 14 through a conduit 39. The shrunk char is recovered in a cyclone separator 40 and, transferred through a conduit 41 intoa quench vessel 15. The hot gases and tar vapors, substantiallyrfree of entrained shrunk char particles, are recovered from the cyclone separator 40 through a conduit 42 and are introduced into the tar condenser vessel 18 along with the primary carbonization tar `vapors for further treatment as will be hereinafter described. Y

The shrunk char particles are cooled'in the char quench vessel 15 to a temperature of about 500 F.V Suitably, the carbonization liquor Vcan be sprayed into the quench vessel 15 to quench the hot char particles while extracting the volatilization heat of ythe liquor.L The quenched char is recovered at about V300 to 400 F. from the char quench vessel 15 through a conduit 43 and introduced intov the briquet kneading apparatus 16. Suitable quantities of pitch binderare introduced into the briquet kneading apparatus 16 through a conduit 44. The mixture of hot char and pitch binder is kneaded in accordance with conventional briquetv making procedures, i.e., at a temperature about 40 F. above the melting temperature-o'f the binder'- pitch.Y

The kneaded mix-ture of charand pitchV binder is recovered from the-kneadingapparatus 16* and introduced into briquet making apparatus 17 whereinV the mixture is pressed at suitable mechanical pressures into uniform shapespreferably from 1/2 to 3 inches in maximum transversal dimension. Formed briquets are recovered from the briquetting apparatus and transferred through a conduit '37 tothe calciner vessel-14 as already described. It is customaryv in briquetting practice to provide slight cooling of the fresh briquets below the melting point of the binder pitchbefore `they are subjected to vigorous mechanical movement.

The present process lautogenously provides the required pitch binder from theV tar which is inherently produced. This process will be brieflydescribed. Referring to the tar condenser vessel 18, tar vapors and non-condensable gases introduced through conduit 31 are quenched byv a vrecirculating liquid spray introduced through a conduit 45. 'I'he liquid spray preferably is the carbonization liquor. Non-condensable gases -are recovered overhead through a conduit 46. The non-condensable gases may be burned to provide the hot gases required for the coal dryer 11. The condensable tar products are recovered along with the condenser spray liquid through -a bottom conduit 47. The condensed liquids are separated in a decanter vessel 19. Supernatant aqueous liquids are recovered and recirculated through the conduit 45 to the condenser vessel 18. Condensed liquid tar is recovered through a conduit 48 and introduced into a distillation vessel Z for separation. The valuable low boiling tar components, e.g., those boiling below about 230 C., are recovered as a distillate product through a conduit 49. A middle boiling tar distillate, for example, boiling from about 230 to 350 or 375 C., is recovered through a conduit 50. 'Ihe high boiling pitch components, for example, those boiling above about 350 to 415 C., are recovered as a bottom product through a conduit 51.

Freshly prepared pitch from non-caking coal has been found to be unsatisfactory as a briquet binder. However, it can be employed as a pitch binder if subjected to a preliminary air blowing treatment at elevated temperatures, for example, 500 to 900 F. The air blowing should be carried out at a suflioient pressure to avoid volatilization of the pitch components. Accordingly, the pitch is transferred from the conduit 51 into the air blowing vessel 21 maintained at an elevated temperature. Air is introduced into the air blowing vessel 21. The pitch is contacted with air for about minutes. An air blown pitch product, suitable as a briquet binder, is recovered through a conduit 52.. The solids-free pitch should have a fixed carbon content (Conradson Carbon) between 25 and 50 percent.

The air blown pitch binder recovered through the conduit 52 may have an excessive melting point. It is desirable that the pitch should become molten at briquet kneading temperatures in order to Wet the char particles completely during the kneading treatment which is customarily carried out with steam heat. Hence the pitch may be blended with middle boiling tar distillate to provide a suitable melting point binder for use in briquet making. A melting point of about 90 to 120 C. is preferred. Accordingly, a portion of the middle boiling tar distillate is withdrawn from the conduit 50 and transferred through a conduit 53 to the binder mixing vessel 22 for blending with air blown pitch to produce a pitch binder of satisfactory melting properties for use in briquet formulations. lThe binder pitch tends to be unstable when stored in liquid form. Hence it is cooled below its melting temperature and stored as a solidied mass. Prior to use,

v the solid pitch is comminuted and blended into the briquet formulation las solid particles.

EXAMPLE The following example is presented to illustrate a material balance and operating conditions for a briquet making plant as illustrated in the drawing. The following data are derived from a briquet plant processing 50 tons per hour of non-caking coal having the properties listed in Table I. The coal is preliminarily crushed to the size distribution listed in Table II.

The coal is introduced into a fluidized dryer 1.1 maintained at a temperature of 400 F. 33,000 cubic feet per minute of gases at 205 F. are recovered from the dryer through conduit 28 containing 510 pounds of entrained solids. 80,420 pounds per hour of dried preheated coal at 400 F. is introduced into a uidized carbonization vessel 12 and maintained therein for 30 minutes. 4,750 cubic feet per minute of air is introduced into the carbonization vessel through a conduit 30 as uidizing and partial combustion gas. A temperature of 925 F. is maintained Within the carbonization Vessel. The linear velocity of the uidizing gases is about 1.65 feet per second.

The carbonization gases, recovered through conduit 31, include:

Pounds per hour Dry tar 12,110 Solids 3,600 Gas 26,000 Water vapor 8,380

50,500 pounds per hour of char at 925 F. is introduced into a char surge vessel 13. The char has the following analysis TABLE IH Char Properties (A) Proximate analysis: Weight percent It is apparent that substantially no agglomeration occurs during carbonization when the particle size analysis of the product char (Table III) is compared with that of the starting coal (Table VII). Y

28,600 pounds per hour of char from conduit 33` are partially burned with 5,680 standard cubic feet per minute of air from conduit 35 to produce a dilute phase suspension of hot char in combustion gases at a temperature of about 2200 F. This dilute phase suspension is blended .with 21,900 pounds per hour of charrfrom conduit 33a to produce a dilute phase stream of char suspended in gases in the conduit 316 at .a temperature of about 1800" F. At this temperature, the char is further devolatilized and experiences a shrinking to effect increased strength. The entire steam of char and hot gases is blown upwardly through a calciner vessel 14. 61,500 pounds per hour of raw briquets are introduced into the top of the calciner vessel. By interchange of heat, the briquets leave the bottom of the calciner vessel at a temperature of about l650 F. and are cooled to produce 52,050 pounds per hour of dry coke. The shrunk char and hot gases are cooled via heat interchange within the calciner vessel to a temperature of 740 F. and withdrawn through a conduit 39. The bulk of the entrained shrunk char is recovered'from a cyclone separator 40 and introduced into a quench drum 15 where it is cooled to about 490 F. for subsequent use in briquet formulation. The effluent stream, recovered through a conduit 42, from the cyclone separator 40 comprises:

Pounds per hour effluent gases and introduced into a condenser 18.

The blended vapor stream recovered from the calciner and carbonization vessel is quenched by water spray to a temperature of about 170 F. The non-condensable gases are recovered at a temperature of about F. and comlows:

prise 59,000 pounds per hour of gas having a net heating value of about 208 B.t.u. per cubic foot. The condensed tar product includes 20,300 pounds per hour of dry tar, 7,860 poundsk per hour of entrained solids Yand 1,185 pounds per hourof moisture. The tar is dehydrated to remove ythe moisture and vintroduced into a distillation tower at a temperature of about 7270? F. Therpitch product boiling above 415 vC. contains 9,080 pounds per solids. This material is introduced into an air blowing vessel 21 maintained at 710 F. About 90 standard cubic feet per minute of air is blown into the air blowing vessel and the eluent vapors are recombined with the lower `boiling distillate fractions of the tar. The product air dryer effluent conduit 28 (510 pounds per hour) prefer- Y hour of pitch and 7,860V pounds per hour of -entrained Y ably is also combined into the briquet formulation. In Y addition, the tine particles of product briquets resulting from abrasion are recovered by screening and are incorporated in the briquet formulation. Typically these briquetrecycle fines will amount to 5,720 pounds per hour.

The shrunk char, recycle coke nes, coal nes from the dryer and pulverized binder pitch are introduced into a briquet kneader at about 260 F., i.e., slightly above the melting pointV of the pitch binder. The briquets are pressed in aY briquet making apparatus 17 and cooled below the pitch melting point for mechanical strength. A total of 61,500 pounds per hour of raw briquets results. These are the briquets which-are introduced into the calciner vessell 14 for coking. f

FURTHER EXAMPLES The following testsareV reported herein to illustrate the effects, respectively, of preliminary ycharV shrinking and of air blown pitch on product metallurgical coke obtained from non-caking coal. l

Test 1.-A briquet formulationwas prepared according to theA present invention. A binder pitch was produced from the low temperature carbonization pitch boiling above 375 C. The pitch wasair blown to a fixed carbon value of 38 percent by- Weight.

from fluidized low temperature carbonization of noncakingY coal was heated to 1800 F. to effect shrinking. The briquet formulation was as follows:

' Parts Y Preshrunk char 80.7 Airr blown pitch Y 11.0 Middle tari distillate 8.3

' One-inch briquets prepared from this formulation, whenV coked to 1800 F., showed a Tumbler Index of 95.8 (when quenched in nitrogen gas) and 94.5 (when quenched in water) Thus briquets of acceptable strengthY can be prepared according to this invention. The Tumbler Index is similar to that described'in ASTM Test Designation` D 294-50, modifiedA to provide' for the one-inchV diameterv briquets'. A

TesrZI-'The same pitch binder andmiddle boiling tar distillate were combined with char Yobtained from uidized low temperature carbonization of the same non-.caking coal used infTest l.V The char was not preshrunk, but instead was formulated into briquets without intervening thermal treatment. Thebriquet formulation was as fol- The pitch was blended Y with middle boiling tardistillate (300 to 375 C.). Char VWest Virgina. The formulation was as follows:

Parts Char .Y i 86.0 Air blown pitch f r 8.4 Middle tar distillate 5.6

The Tumbler Index of the resulting coked briquets was 55.1. Thus the improved coke strength achieved by preliminary char shrinking is clear when the results of Tests l and 2 are compared.

Test ia-Briquets were prepared from the same starting ingredients of Test 2 with the addition of a minor portion of caking coal. The caking coal was a Pittsburgh Seam high volatile, strongly caking coal obtained in northern Parts Char 73.0 Air blown pitch 7.1 Middle tar distillate 5.7 Caking coal 14.2

The Tumbler Index of the resulting coked briquets was 80.0. Hence it is seen that improved briquets can be prepared from the char product of non-caking coal when a minor portion of strongly caking coalV is incorporated into the formulation. i However, the briquet strength achieved by addition of caking coal to the briquetis not as high Vas that resulting from the use ofshrunk char.

'Test 4.-Briquets` were prepared from a formulation comprising char from lluidized low temperature carbonization ofV a non-caking coal and a binder pitch produced from the low temperature carbonization pitch boiling above 375 C. The char had been heated to l800 F. to effect shrinking, but the pitch was not air blown, in contrast to the pitch employedin the rst three tests. The formulation was as follows:

e Parts Preshrunk char p 85.0 Pitch (not air blown) 15.0

TheTurnbler Index of the resulting coked briquets was 85.9. Thus, while the use of preshrunlrcharV effected a substantial improvement, the'use of non-air blown pitch` prevented attaining the high Tumbler Index obtained in Y ,Test l. f

While fluidized low temperature carbonization has been described in the foregoing specification asv a preferred processing technique, nevertheless, other forms of low temperature carbonization may be employed, preceded or followed by crushing of the solids to a particle size' suitable for effective shrinking treatment and heat interchange with'pressed briquets.

Accordingto the provisions of the patent statues, we-

have explained the principle,preferred construction and mode of operation of our invention and have illustrated and described what we now consider to represent its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustratedl and described. f

We claim:

1. The method of preparing `coked vbriquets' from a non-caking `coal. which comprises carbonizing said nonycaking coal to produce gas, tar and char, heating said char in particulate form to an elevated. temperature abovethe carbonization temperature at which said char was generated to eect shrinkingof the char, recovering ahigh boiling pitch from said tar,v subjecting said pitch Yto air blowingat an elevated temperature to therebyL increase its fiXedcarbon-content, forming raw briquetsfrom said preshrunk char and said air blown'pitch at low temperature, and thereafterV cokingy said raw briquets. 2. The method of preparing coked briquets from a non-caking coal which comprises carbonizing said noncaking `coal in a uidized state at a-temperature'between' about 800-and 1100 F. to produce gas,`tar and char,

heating said char in particulate form to la temperature between about 1350 and 1800 F. 'to effect shrinking of' the char, h'actionally distilling said tar to recover a pitch boiling above about said 350 to 415 C. and a distillate fraction boiling from about 7.30 to 375 C., subjecting said pitch to air -blowing at a temperature between 500 and 900 F. to increase its fixed carbon content to between 25 and 50 percent, blending said pitch with at least a portion of said distillate fraction to produce a material having 1a melting point between 90 and 120 C., forming raw briquets from said preshrunk char and said Iblended material, at a temperature above the melting point of said blended material, and thereafter coking said raw briquets.

3. In the .process of preparing coked briquets from char and pitch obtained by the carbonization of a noncaking coal at a low temperature, the improvement which comprises heating said char in particulate form to an elevated temperature above the carbonization temperature at which said char was generated to effect shrinking of the char, subjecting said pitch to air blowing at an elevated temperature to thereby increase its xed carbon content to between 25 and 50 percen-t, thereafter incorporating said preshrunk char and said air blown pitch in a Ibriquet formulation, forming briquets from said lformulation, and thereafter cofking said briquets.

4. In the process of preparing coked briquets from char and pitch obtained by the carbonization of noncaking coal at a low temperature, the improvement which comprises heating said char in particulate form to an elevated temperature above the carbonization temperature at which said char was vgenerated to eiect shrinking `of the char, increasing the fixed carbon content of said pitch to between 25 and 50 percent, thereafter incorporating said preshrunk char and said pitch in a briquet formulation, forming briquets from said formulation, and thereafter coking said briquets.

References Cited in the file of this ,patent UNITED STATES PATENTS 2,095,190 Heuscher Oct. 5, 1937 2,203,645 Rey-nerd June 4, 1940 2,594,226 Shea Apr. 22, 1952 2,683,107 Juel July 6, 1954 2,864,760 Croy Dec. 16, 1958 2,985,577 Geller et al May 23, 1961 

1.THE METHOD OF PREPARING COKED BRIQUETS FROM A NON-CRACKING COAL WHICH COMPRISES CARBONIZING SAID NONCAKING COAL TO PRODUCE GAS, TAR AND CHAR, HEATING SAID CHAR IN PARTICULATE FROM TO AN ELEVATED TEMPERATURE ABOVE THE CARBONIZATION TEMPERATURE AT WHICH SAID CHAR WAS GENERATED TO EFFECT SHRINKING OF THE CHAR, RECOVERING A HIGH BOILING PITCH FROM SAID TAR, SUBJECTING SAID PITCH TO AIR BLOWING AT AN ELEVATED TEMPERATURE THEREBY INCREASE ITS FIXED CARBON CONTENT, FORMING RAW BRIQUETS FROM SAID PRESHRUNK CHAR AND SAID AIR BLOW PITCH AT LOW TEMPERATURE, AND THEREAFTER COKING SAID RAW BRIQUETS. 